Limit Analysis of a historical iron arch bridge. Formulation and computational implementation.

In the paper an innovative formulation of a FEM computational model for the analysis of elastoplastic 3D truss-frame structures is developed within the framework of the Theory of Plasticity and Limit Analysis. Reference application is made to a historical iron arch bridge. Original computational features implemented in the solving algorithm allow for tracking the limit structural behavior of the bridge, by reaching convergence with smooth runs up to the true limit load and by tracing the corresponding collapse displacements. This is achieved disregarding for the considerable number of dofs of the whole structural model, ranging in the order of thirteen thousands.